Downlink power control for multiple downlink time slots in TDD communication systems

ABSTRACT

A method for downlink power control for use in a spread spectrum time division communication system having time slots for communication, implemented in a user equipment, includes receiving data in a command per coded composite transport channel (CCTrCH) transmitted over a plurality of time slots. An interference power for each time slot of the plurality of time slots is measured and a single power command for the entire CCTrCH is transmitted in response to a signal to interference ratio of the received CCTrCH and the measured interference power measurement for each time slot. A subsequent data is received in the CCTrCH communication having a transmission power level for each downlink communication time slot set individually in response to the interference power measurement for that time slot and the single power command for the entire CCTrCH.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.09/845,803, filed Apr. 30, 2001, which claims the benefit of U.S.provisional application No. 60/200,756 filed May 1, 2000, which areincorporated by reference as if fully set forth.

BACKGROUND

This invention generally relates to spread spectrum time division duplex(TDD) communication systems. More particularly, the present inventionrelates to a system and method for controlling downlink transmissionpower within TDD communication systems.

Spread spectrum TDD systems carry multiple communications over the samespectrum. The multiple signals are distinguished by their respectivechip code sequences (codes). Referring to FIG. 1, TDD systems userepeating frames 34 divided into a number of time slots 37 ₁-37 _(n),such as fifteen time slots. In such systems, a communication is sent ina selected time slot out of the plurality of time slots 37 ₁-37 _(n)using selected codes. Accordingly, one frame 34 is capable of carryingmultiple communications distinguished by both time slot and code. Thecombination of a single code in a single time slot is referred to as aphysical channel. Based on the bandwidth required to support acommunication, one or multiple physical channels are assigned to thatcommunication.

Most TDD systems adaptively control transmission power levels. In a TDDsystem, many communications may share the same time slot and spectrum.While user equipment (UE) 22 is receiving a downlink transmission from abase station, all the other communications using the same time slot andspectrum cause interference to the specific communication. Increasingthe transmission power level of one communication degrades the signalquality of all other communications within that time slot and spectrum.However, reducing the transmission power level too far results inundesirable signal to noise ratios (SNRs) and bit error rates (BERs) atthe receivers. To maintain both the signal quality of communications andlow transmission power levels, transmission power control is used.

The standard approach to TDD downlink power control is a combination ofinner and outer loop control. In this standard solution, the UEtransmits physical layer transmit power control (TPC) commands to adjustthe base station transmission power. A base station sends a transmissionto a particular UE. Upon receipt, the UE measures the signalinterference ratio (SIR) in all time slots and compares this measuredvalue to a SIR_(TARGET). This SIR_(TARGET) is generated from the BlockError Rate (BLER) signaled from the base station.

As a result of the comparison of the measured SIR value with theSIR_(TARGET), the UE transmits a TPC command to the base station. Thestandard approach provides for a TPC command per coded compositetransport channel (CCTrCH). The CCTrCH is a physical channel whichcomprises the combined units of data for transmission over the radiointerface to and from the UE or base station. This TPC command indicatesto the base station to adjust the transmission power level of thedownlink communication. The base station, which is set at an initialtransmission power level, receives the TPC command and adjusts thetransmit power level in all time slots associated with the CCTrCH inunison.

This approach to TDD downlink power control works well as long as theinterference in each time slot is the same. Unfortunately, in mostcases, the interference in each time slot is different. A smalldifference may be acceptable due to the averaging effect of theinterleaving, but larger differences cause degradation due tothresholding effects in the receiver. This requires the receiver to havea wider dynamic range and unnecessarily high transmit power in some timeslots. An adjustment made to the base station SIR_(TARGET) for all timeslots based on the error value may create an unbalanced increase ordecrease of the power level. In other words, those time slots where thepower level was lower than the initial value of the base station will beadjusted even lower when the calculated error value was higher than theSIR_(TARGET). These low level power time slots may then be eliminatedfrom detection, thereby the transmission will be degraded. The same istrue for those time slots in which the power level was higher than theSIR_(TARGET) of the base station. When the detected error rate is lowerthan the SIR_(TARGET), the higher power level time slots will beincreased, thereby creating interference with other channels on thesystem.

Accordingly, there is a need to have an approach to TDD downlink powercontrol which adjusts the power level of each slot individually.

SUMMARY

The present invention is a method and system for controlling downlinktransmission power levels in a spread spectrum time divisioncommunication system having frames with time slots for communication,which receives at a user equipment (UE) a downlink communication from abase station and determines an error rate of the received communication.The UE then produces power level adjustments for each of the time slotsbased in part on the error rate and transmits an uplink communication tothe base station which includes the power level adjustment for each ofthe time slots. In response to the power level adjustments transmissionpower level is set for each time slot in the downlink communication.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 illustrates time slots in repeating frames of a TDD system.

FIG. 2 illustrates a simplified wireless TDD system.

FIGS. 3A and 3B illustrate block diagrams of a UE and base station,respectively.

FIG. 4 illustrates a flow diagram of a first embodiment.

FIG. 5 illustrates a flow diagram of a second embodiment.

FIG. 6 illustrates a block diagram of the base station made inaccordance with the second embodiment.

FIG. 7 illustrates a flow diagram of a third embodiment.

FIG. 8 illustrates a flow diagram of a fourth embodiment.

FIG. 9 illustrates a flow diagram of a fifth embodiment.

FIG. 10 illustrates a flow diagram of a sixth embodiment.

FIG. 11 illustrates a flow diagram of a seventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The preferred embodiments will be described with reference to thedrawing figures where like numerals represent like elements throughout.

FIG. 2 illustrates a simplified wireless spread spectrum code divisionmultiple access (CDMA) or time division duplex (TDD) communicationsystem 18. The system 18 comprises a plurality of node Bs 26, 32, 34, aplurality of radio network controllers (RNC), 36, 38, 40, a plurality ofUEs 20, 22, 24 and a core network 46. The plurality of node Bs 26, 32,34 are connected to a plurality RNCs 36, 38, 40, which are, in turn,connected to the core network 46. Each Node B, such as Node B 26,communicates with its associated user equipment 20-24 (UE). The Node B26 has a single site controller (SC) associated with either a singlebase station 30 ₁, or multiple base stations 30 ₁ . . . 30 _(n).

Although the present invention is intended to work with one or more UEs,Node Bs and RNCs, for simplicity of explanation, reference will be madehereinafter to the operation of a single UE in conjunction with itsassociated Node B and RNC.

Referring to FIG. 3A, the UE 22 comprises an antenna 78, an isolator orswitch 66, a modulator 64, a demodulator 68, a channel estimation device70, data estimation device 72, a transmit power calculation device 76,an interference measurement device 74, an error detection device 112, aprocessor 111, a target adjustment generator 114, a reference channeldata generator 56, a data generator 50, and two spreading and trainingsequence insertion devices 52, 58.

The UE 22 receives various radio frequency (RF) signals includingcommunications from the base station 30 ₁ over the wireless radiochannel using an antenna 78, or alternatively an antenna array. Thereceived signals are passed through a T/R switch 66 to a demodulator 68to produce a baseband signal. The baseband signal is processed, such asby a channel estimation device 70 and a data estimation device 72, inthe time slots and with the appropriate codes assigned to the UEs 22communication. The channel estimation device 70 commonly uses thetraining sequence component in the baseband signal to provide channelinformation, such as channel impulse responses. The channel informationis used by the data estimation device 72, the interference measurementdevice 74 and the transmit power calculation device 76. The dataestimation device 72 recovers data from the channel by estimating softsymbols using the channel information.

Prior to transmission of the communication from the base station 30 ₁,the data signal of the communication is error encoded using an errordetection/correction encoder 112. The error encoding scheme is typicallya cyclic redundancy code (CRC) followed by a forward error correctionencoding, although other types of error encoding schemes may be used. Asthose skilled in the art know, the data is typically interleaved overall of the time slots and all codes.

Using the soft symbols produced by the data estimation device 72, theerror detection device 112 detects errors in the frame. Each time aframe is determined to have an error, a counter is incremented. Thiscounter value becomes the block error rate (BLER). A processor 111 inthe UE 22 typically determines a target signal to interference ratio SIRvalue based on the measured BLER and determines a signal to interferenceratio SIR_(UE) for all time slots. Based on the SIR_(UE), the processor111 determines the adjustment of the base station transmit power bycomparing the SIR_(UE) with the SIR_(TARGET). Based on this comparison,a TPC command is generated by the target adjustment generator 114 foreach time slot. Each TPC command is subsequently sent to the basestation.

In a first embodiment of the present invention, the target adjustmentgenerator 114 in the UE 22 generates and transmits TPC commands in eachtime slot of the CCTrCH. The TPC command in each time slot indicates tothe base station 30 ₁ to adjust the downlink transmission power levelfor each time slot. The uplink physical channel comprises these TPCcommands for each slot associated with the CCTrCH, and is communicatedto the base station for processing. These TPC commands may betransmitted in a single uplink physical channel, or spread over severaluplink physical channels.

Referring to FIG. 3B, a base station made in accordance with the firstembodiment of the present invention is illustrated. The antenna 82 or,alternately, antenna array of the base station 30 ₁ receives various RFsignals including the TPC commands. The received signals are passed viaa switch 84 to a demodulator 86 to produce a baseband signal.Alternatively separate antennas may be used for transmit or receivefunctions. The baseband signal is processed, such as by a channelestimation device 88 and a data estimation device 90, in the time slotsand with the appropriate codes assigned to the communication burst ofthe UE 22. The channel estimation device 88 commonly uses the trainingsequence component in the baseband signal to provide channelinformation, such as channel impulse responses. The channel informationis used by the data estimation device 90. The data information isprovided to the transmit power calculation device 98 by processor 103.

Processor 103 converts the soft symbols produced by the data estimationdevice 90 to bits and extracts the TPC commands for each time slotassociated with the CCTrCH. The transmit power calculation device 98combines the TPC commands with the SIR_(target) to determine thetransmission power for each time slot associated with the CCTrCH.

Data to be transmitted from the base station 30 ₁ is produced by datagenerator 102. The data is error detection/correction encoded by errordetection/correction encoder 110. The error encoded data is spread andtime-multiplexed with a training sequence by the training sequenceinsertion device 104 in the appropriate time slot(s) and code(s) of theassigned physical channels, producing a communication burst(s). Thespread signal is amplified by an amplifier 106 and modulated bymodulator 108 to radio frequency. The gain of the amplifier iscontrolled by the transmit power calculation device 98 to achieve thedetermined transmission power level for each time slot. The powercontrolled communication burst(s) is passed through the isolator 84 andradiated by the antenna 82.

A flow diagram illustrating the method of downlink power control inaccordance with the first embodiment of the present invention is shownin FIG. 4. The UE 22 receives a downlink signal from the base station 30₁, (step 401), which is then processed by the UE 22 (step 402). The UE22 then determines the SIR for each time slot of the CCTrCH and comparesit to the SIR_(target) (step 403). The UE then generates a TPC commandfor each time slot (step 404). The TPC commands are transmitted to thebase station 30 ₁ associated with the UE 22, (step 405), which adjuststhe transmission power per time slot of the CCTrCH (step 406).

The use of TPC commands for every time slot provides the communicationsystem with a simple method of equalizing the signal to interferenceratio (SIR) in all downlink slots. Since the interference level indifferent time slots is generally different, this method of the firstembodiment of the present invention accounts for this difference andgenerates a separate TPC command for each time slot to adjust the powerlevel of each time slot in the downlink signal.

A second embodiment of the present invention presents an alternativeapproach for balancing the adjustment to the power level individually ineach time slot, during downlink transmission by utilizing the time slotinterference data from each time slot, a measured downlink interferencesignal code power (ISCP). This ISCP measurement is made by the UE 22from time to time, determined by interference rate of change and theamount of interference difference that can be tolerated by the UE 22without degradation.

This second embodiment utilizes the time slot interference data fromeach time slot to equalize the SIR in different slots to counter thefact that the interference is different in each slot. As will beexplained in greater detail hereinafter, a TPC command per CCTrCH alongwith interference information for each slot are used to adjust thetransmission power. The difference between the interference in differenttime slots modifies the values that are obtained from the TPC commands.Therefore, although the interference in each time slot may be different,use of the ISCP information maintains approximately the same SIR in alltime slots.

The UE 22, at each frame, sends a TPC command that corresponds to theaverage SIR in all time slots that belong to the same CCTrCH. The basestation 30 ₁, then constructs an average transmit power per CCTrCH basedon the received TPC commands. As will be explained in greater detailhereinafter, the base station 30 ₁, then modifies the average power toobtain the transmit power for each time slot for the CCTrCH, based onthe relevant interference data and the time slot mapping used. It shouldbe noted that this alternate approach allows the use of multiplespreading factors.

Referring to FIG. 6, a base station made in accordance with this secondembodiment is illustrated. The transmit power calculation device 698within the base station 30 ₁ initializes the downlink power controlapproach of the second embodiment by combining the interference andspreading code information to estimate equivalent power obtained fromthe TPC commands P.P =(F/N)Σ_(j) I _(j)Σ_(k)1/S _(jk)  Equation 1where j and k refer to time slot and physical channel respectively; N isthe total number of physical channels at spreading factor of 16 in oneslot. I_(j) represents the interference in time slot j, j=1, . . . N; Fis a scaling factor and 1/S_(jk) is the spreading factor.

The transmit power calculation device 698 then, using the interferenceper time slot and the mapping information stored in the base stationdata base 696, calculates the scaling factor F in accordance with thefollowing equation:F=NP/(Σ_(j) I _(j)Σ_(k)1/S _(jk)  Equation 2and the transmit power for all physical channels P_(jk) according toEquation 3:P _(jk) =FI _(j)/1/S _(jk)  Equation 3The power per time slot is defined as:P _(j) =FI _(j)Σ_(k)1/S _(k)  Equation 4During steady state operation, the transmit power calculation device 698updates the scaling factor F for each physical channel whenever newdownlink interference signal code power (ISCP) measurements I for eachtime slot associated with the particular downlink CCTrCH are available.In order for the transmit power calculation device 698 to calculate thescaling factor F, the spreading factor for each physical channel isused. The transmit power calculation device 698 calculates the transmitpower using the ISCP measurement I which is made available to thetransmit power calculation device 698 either periodically or whenevernew interference information warrants an update.

When a new ISCP measurement I is made, the measurement is transferred tothe base station 30 ₁ for calculation of the transmit power for eachphysical channel. If a new ISCP measurement I is not available, the TPCcommand from the UE 22 is used to modify P in the standard way, and thetransmit power for all physical channels P_(jk) is calculated therefrom.

Referring to FIG. 5, a flow diagram of downlink power control inaccordance with this second embodiment is illustrated. The UE 22receives a downlink communication from the base station 30 ₁ (step 501).If the UE 22 determines an updated ISCP measurement is required, the UE22 makes an ISCP measurement for each time slot in the downlinkcommunication and forwards the new ISCP measurements to the base station30 ₁ (step 502). Otherwise the UE 22 generates a TPC command andforwards it to the base station (step 503). The base station 30 ₁calculates the scaling factor for all physical channels (step 504) usingthe TPC command or ISCP measurement from the UE 22. The transmissionpower level for each time slot is then calculated by the base station 30₁ (step 505) and the downlink signal updated accordingly (step 506).

It should be noted that even though the second embodiment has beendescribed with the base station storing all required information andconducting all calculations on its own, the Node B 26 and RNC 36 mayperform this function instead. Referring to FIG. 6, a flow diagramillustrates a third embodiment downlink power control system wherein theNode B 26 and RNC 36 are involved. The UE 22 receives a downlinkcommunication from the base station 30 ₁ (step 701). If the UE 22determines an updated ISCP measurement is required, the UE 22 makes anISCP measurement for each time slot in the downlink communication andforwards the new ISCP measurements to the RNC 36 (step 702). Otherwisethe UE 22 generates a TPC command and forwards it to the base stationRNC 36 (step 703). If the downlink power control system is set up tohave the RNC 36 calculate the transmit power, the transmit power foreach time slot is calculated by the RNC 36 (step 704) and then forwardedto the Node B 26 in order to update the base station 30 ₁ downlinksignal (step 706). If the Node B 26 is setup to calculate the transmitpower, the RNC 36 transmits the ISCP or TPC connected to the Node B 26(step 705) where the transmit power for each time slot is calculated(step 706).

A fourth embodiment for downlink power level control utilizes time slotinterference data similar to that disclosed in the second embodimentabove. In this approach though, time slot interference is calculatedfrom knowledge of the allocated downlink physical channels by the basestation 30 ₁, and loading information and path loss from all neighborbase stations to the UE 22, rather than requiring explicit ISCPmeasurements from the UE 22. Each base station, such as base station 30₁, knows all allocated channel configurations for the UE's 22 specificbase station 30 ₁, as well as other neighbor base stations 30 ₂ . . . 30_(n). Obviously, if there is only one base station 30 ₁, no additionalinformation from other base stations is required. The base station 30 ₁must also know the load and path loss information of all neighboringbase stations from the neighboring base stations to the UE 22.

When there are multiple base stations, the UE 22 typically measures theprimary common control physical channel (PCCPCH) power of base stationsunder the control of its base station's Node B 26 and all other basestations. The base station 30 ₁ uses the known PCCPCH transmission powerand the power measurement of same as received by the UE to estimate thepath loss between the UE and each of the neighbor base stations.

Referring again to FIG. 6, the base station database 696 has storedtherein the loading information which specifies the physical channels inthe neighbor base station by time slot. This loading information iscombined with the PCCPCH. The received signal code power (RSCP) for theparticular base station is used to estimate the interference effect ofthe neighboring base station. From these calculations, the interferenceat the UE 22 can be calculated. For a non-multiple user detection (MUD)UE, the interference of its associated base station and the interferenceof the neighboring base stations are used to calculate this value. For aMUD UE, interference generated by the UE's associated base station isexcluded from the UE interference value.

The estimated interference, I(n), using known loading information iscalculated by the transmit power calculation device 698 as:I(n)=ΣP _(J)(n)L _(j)(n)  Equation 5Applying this estimated interference value to Equations 1 through 4, thetransmit power calculation device 698 calculates the transmit power foreach time slot.

Referring to FIG. 8, a flow diagram of downlink power control inaccordance with this fourth embodiment is illustrated. The base station30 ₁ calculates the estimated interference I for each time slot (step801) and then calculates the transmission power level for each time slot(step 802) using Equations 1 thru 5 above, which updates the basestation downlink signal is updated (step 803).

Again it should be noted that the node B 26 and RNC 36 may also conductthe function of storing all required information and calculating theestimated interference and the transmit power for each time slot.Referring to FIG. 9, a flow diagram of downlink power control inaccordance with this fifth embodiment is illustrated. The RNC 16calculates an estimated interference I for each time slot (step 901). Ifthe system is configured such that the node B 26 calculates the transmitpower, the RNC 36 forwards the estimated interference I to the node B 26(step 902) where the transmit power for all physical channels iscalculated (step 903), and the base station downlink signal updated(step 904). Otherwise the RNC 36 calculates the transmission power foreach the slot (step 903).

Since physical channels are allocated by the RNC in advance of actualphysical transmission, it is possible for a Node B to calculate theexpected UE interference for the frame being transmitted in real time.The real time interference calculation allows for the correcttransmission power for each time slot for the frame being transmitted.

A sixth embodiment of the present invention utilizes the combination ofthe measured and estimated interference approaches disclosed above tocontrol downlink power. In this approach, the base station 30 ₁ combinesweighted interference values for both the estimated interference andmeasured interference to calculate the transmission power per time slotof the CCTrCH. For MUD UE, the relevant interference (that affectsdetection performance) in each slot is denoted as:

$\begin{matrix}{{I_{D}(n)} = {\sum\limits_{{allj} \neq 0}{{P_{j}(n)}{L_{j}(n)}}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$where P_(j)(n) is the transmission power of base station j at time n ina certain slot, P₀, being the transmission power of the UE's basestation 30 ₁. L_(j)(n) denoting the corresponding path loss. For anon-MUD UE, the relevant interference is denoted as:

$\begin{matrix}{{I_{D}(n)} = {\sum\limits_{{all}\mspace{14mu} j}{{P_{j}(n)}{L_{j}(n)}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$The measured interference I_(D)(n), though, will be reported by the UEas an ISCP measurement. Equations 5 and 6 are merely illustrative ofthis interference present in the communication system:

The estimated interference is denoted as:I(n)=ΣP _(j)(n)L _(j)(n)  Equation 7Where the summation is carried over all known interferers whose load andpath loss to the UE are known. Similar to the fifth embodiment, loadinformation is known by the base station 30 ₁ for all j. Anyinterference from a load UE not known is designated as the residualinterference I_(j)(n), I_(f)(n)=I(n)−I_(D)(n). From each of theseinterference values, the transmission power device 698 combines them togenerate a more accurate interference power value to be used in theestimation of the downlink transmission power for each time slot,defined by Equations 1 thru 4. The combined interference power value isdefined as:I=αI _(f) +βI+γI _(D), α+β+γ=1  Equation 8where coefficients α, β and γ are determined per system or even per slotaccording to measurement delays or existence of foreign base stations.

Illustrated in FIG. 10 is a flow diagram of the downlink power controlsystem in accordance with the sixth embodiment. The base station 30 ₁receives a communication from the UE₂₂ including an ISCP interferencemeasurement I_(D) for each time slot (step 1001). The transmission powercalculation device 698 then calculates an estimated interference value Iusing information stored in the base station database 698 (step 1002). Aresidual interference value I_(F) is then calculated by the transmissionpower calculation (step 1003). The transmission power calculation devicethen combines the three interference values I_(D), I, I_(F) (step 1004)and calculates the transmission power for each time slot of the downlinkcommunication (step 1005).

Similar to the previous embodiments, the RNC 36 and Node B 26 maycalculate the transmission power for each time slot as described abovein a seventh embodiment. Referring to FIG. 11, a flow diagram of thisembodiment is illustrated. The RNC 36 receives a communication from theUE 22 including an ISCP interference measurement I_(D) for each timeslot. (step 1101) The RNC 36 then calculates an estimated interferencevalue Î using information stored in the RNC 36 (step 1102) and aresidual interference value I_(F) (step 1103). The RNC 36 then combinesthe three interference values I_(D), Î, I_(F) (step 1104) and calculatesthe transmission power for each time slot of the downlink communicationusing Equations 1 thru 4 (step 1106) and forwards them to the basestation 30 ₁ by way of the node B 26. (step 1107) If the downlink powercontrol system is set up to allow the node B 26 to calculate thetransmission power for each time slot, the RNC 36 forwards the combinedinterference value I to the node B 26 (step 1105), which calculates thetransmission power for each time slot (step 1106) and forwards them tothe base station (step 1107).

The benefit of providing a system which utilizes a measured ISCP valueand an estimated interference value to calculate the transmission powerfor each time slot of the downlink communication is two fold: 1) thesystem provides flexibility to the calculation of transmission power ina case where the required information is not known; and 2) the systemprovides a more accurate estimate of the interference present in thecommunication system.

What is claimed is:
 1. A method for downlink power control for use in aspread spectrum time division communication system having time slots forcommunication, implemented in a user equipment, comprising: receivingdata in a command per coded composite transport channel (CCTrCH)transmitted over a plurality of time slots; measuring an interferencepower for each time slot of the plurality of time slots; transmitting asingle power command for the entire CCTrCH in response to a signal tointerference ratio of the received CCTrCH and the measured interferencepower measurement for each time slot; and receiving a subsequent data inthe CCTrCH communication having a transmission power level for eachdownlink communication time slot set individually in response to theinterference power measurement for that time slot and the single powercommand for the entire CCTrCH.
 2. The method of claim 1 wherein thetransmission power level of the subsequent data in the CCTrCHcommunication is set by establishing a transmit power level in responseto the single power command for the entire CCTrCH and modifying thetransmit power level in each time slot in response to the interferencepower measurement of that time slot.
 3. The method of claim 1 whereinthe interference power measurements are interference signal code power(ISCP).
 4. A method for downlink power control for use in a spreadspectrum time division communication system having time slots forcommunication, implemented in a base station, comprising: receiving asingle power command for an entire command per coded composite transportchannel (CCTrCH) and an interference power measurement for each timeslot of the CCTrCH which is transmitted over a plurality of time slots;and transmitting data in the CCTrCH over the plurality of time slots andthe CCTrCH having a transmission power level for each time slot setindividually in response to the interference power measurement for thattime slot and the single power command for the entire CCTrCH.
 5. Themethod of claim 4 wherein the transmission power level of the CCTrCHcommunication is set by establishing a transmit power level in responseto the single power command for the entire CCTrCH and modifying thetransmit power level in each time slot in response to the interferencepower measurement of that time slot.
 6. The method of claim 4 whereinthe interference power measurements are interference signal code power(ISCP).
 7. A method for downlink power control for use in a spreadspectrum time division communication system having time slots forcommunication, implemented in a user equipment, comprising: receiving adownlink command per coded composite transport channel (CCTrCH);transmitting transport power control (TPC) commands, wherein one TPCcommand is transmitted per entire downlink CCTrCH channel; which TPCcommand corresponds to the average signal to interference ratio (SIR) inall time slots that belong to the same CCTrCH channel; performing adownlink interference signal code power (ISCP) measurement for each timeslot in the received CCTrCH channel; transmitting the ISCP measurementsto a base station; and receiving, in response to the transmission of theISCP measurement and the TPC command for the entire CCTrCH channel, adownlink CCTrCH communication having an individual transmission powerlevel for each downlink CCTrCH channel time slot.